The fundamental problems to be investigated concern how progenitor cells become committed to differentiate into specific cell types and establish the functional linkages basic to the development of a multicellular organism. To lay the groundwork for understanding how cells interact, either over long distances via diffusible substances or on a short range as mediated by cell contact, we have chosen as a model system, the slime mole amebae, Dictyosteleum discoideum. Our immediate approach to understanding how cells process sensory information into a locomotory response leading to specific intercellular contact is to study the regulation of the plasma membrane cAMP receptor. This receptor apparently regulates cell sensitivity to, and production of, cAMP pulses, the chemotactic signal for these amebae. Our experiments are designed to elucidate the factors which regulate the level of these receptors and to isolate and characterize the cAMP receptor. Toward this end we will employ both biochemical and genetic techniques.